1. Field of the Invention
This invention relates to a speed control device for a moving member, and, more particularly, it is concerned with a device for controlling speed of a moving member wherein a moving condition of the member to undergo a predetermined movement is first detected, and if it differs from a predetermined moving speed, a control operation is effected to rectify this discrepancy between the predetermined moving speed and the actual moving speed.
2. Description of the Prior Art
Heretofore known methods which have been used for forming a spiral track on a disc-shaped recording carrier or medium, or following up the spiral track on the recording carrier have been such that a recording or reproducing head is caused to shift in the radial direction of the recording carrier at a constant speed relative to a speed of the abovementioned recording carrier.
Known as such recording carriers are acoustic record discs, magnetic discs, and so on. In such conventional recording carrier, as the interval between the adjacent tracks is broad, the error in the pitch derived from the mechanical precision in the advancing mechanism of the recording or reproducing head can be reduced to a negligible extent by improving such mechanical precision.
However, in the video-discs with image informations recorded thereon, the development of which has flourished in recent years, the pitches between the adjacent tracks in the radial direction of the video-disc are narrower than that of acoustic record discs by approximately a few tenths of a fraction in view of a large amount of informations being recorded. In this consequence, errors in the mechanical precision of the advancing mechanism of the recording or reproducing head have become unacceptable. That is to say, in the above-described video-disc, as the pitch of the signal track is approximately 1 micron or so, even when the mechanical precision of the advancing mechanism of the head is improved, the mechanical errors to be derived from the advancing mechanism have been unable to be neglected.